This application relates to a hollow fan blade for a gas turbine engine.
Gas turbine engines may be provided with a fan for delivering air to a compressor section. The fan also delivers bypass air into a bypass duct. From the compressor section, the air is compressed and delivered into a combustion section. The combustion section mixes fuel with the air and combusts the combination. Products of the combustion pass downstream over turbine rotors which are driven to rotate and in turn rotate the compressor and fan.
The fan may include a rotor having a plurality of blades.
One type of fan blade is a hollow fan blade having an internal cavity defined forwardly of a spar, which defines one side of the fan blade. Some filler material, such as a honeycomb filler, is received within the cavity, and a cover is placed over the honeycomb material, closing off the cavity. In the prior art, the cover was not structural, and was made to be much thinner than the thickness of the spar wall. In one example, the cover was one-sixth the thickness of the spar wall. Thus, the spar wall provided all structural integrity for the central areas of the fan blade. The blades are subject to a number of challenges, including internal stresses that vary along the length of the fan blade.
Recently, fans have been provided with a gear drive from a turbine. This has enabled a dramatic increase in the fan's diameter. With this enlarged fan blade, there are much greater structural challenges along the fan blade. In addition, the larger fan blade is more likely to be impacted by debris, or by bird strikes.